This invention relates generally to agricultural balers and, more particularly, to such balers which are fitted with density control mechanisms.
It is common in the agricultural baler art to control the density of a bale being formed by adjusting the position of one or more so-called tension rails which, in effect, define the walls of a bale chamber in which a bale is formed. Such a baler is disclosed in U.S. Pat. No. 4,489,648 and the mechanism for adjusting one or more of the tension rails of the bale chamber is simplified, compared with prior mechanisms.
The density control mechanism of U.S. Pat. No. 4,489,648 operates satisfactorily under normal operating conditions but problems can arise when handling crop material having a high moisture content because the increased friction between the crop material and the tension rails in the bale chamber can result in plugging of the machine, possibly with the attendance breakage of shear bolts in the drive line to the baler plunger. The rectification of either or both of these events results in down time of the machine which is unacceptable.
According to the present invention there is provided a baler comprising a bale chamber having at least one wall movable generally laterally of the bale chamber to vary the cross-sectional area thereof and hydraulic actuator means operable to move the laterally movable bale chamber wall. The improvement comprises hydraulic sensor means coupled to, and operable to sense the load on, the movable wall of the bale chamber and to control the actuator means when that load exceeds a predetermined value, whereby the cross-sectional area of the bale chamber is increased to relieve said load. This allows the baler to produce bales of substantially constant density irrespective of varying crop conditions.
Thus the present invention provides means for sensing the load on a wall of the bale chamber and for increasing the cross-sectional area of the bale chamber when that load exceeds a predetermined value. Accordingly, the load is then relieved and continual movement through the bale chamber of a bale being formed is achieved, thereby preventing plugging of the machine and/or the breakage of shear bolts in the baler plunger drive line.
Preferably, the hydraulic sensor means is connected to a source of pressure fluid through a non-return valve, the same source of pressure fluid also being connected to the hydraulic actuator means operable to adjust the position of one or more walls of the bale chamber, and itself being connected to a resrvoir via a pressure relief valve. The sensor means is conveniently in the form of a pair of hydrualic cylinders each connected between a frame member of the machine and the movable wall of the bale chamber. The hydraulic cylinders are connected in parallel. The sensor means may be associated with the top wall of the bale chamber and may be arranged to sense the load on that wall in the general direction of movement of crop material through the bale chamber.